The image tone of black-and-white photographic prints made by an automated processor is dependent, at least to some extent, on the paper employed and the number of prints made with the batch of chemicals used. Prior to this invention, the image tone of a small initial number of prints for some developer incorporated papers generally had a blue tone which, after about 25 or 50 or other such small number of prints, became noticeably warmer, i.e., more yellow. Furthermore, prior to this invention, it had been noted that over the useful life of the chemicals previously available, that the image tone of the prints produced could vary somewhat, and in a non-controlled fashion.
In some instances, these operating factors may be considered to be less than optimum. For example, if multiple prints of a machinery part or similar device are to be made for some professional purpose, e.g., advertising, or publicity, it may be desired by the customer to have an image tone which is more uniformly colder than what was heretofore available. More specifically, the customer may wish to have the image tone remain relatively constant within an acceptable range, over say about 1000 prints, so that each recipient of a print copy receives about the same print as every other recipient. The present invention satisfies this need.
Fast black and white photographic print processing is achieved by the aforementioned commercial processor, which has been on the market for some time. The processor is designed to process black-and-white papers that have a developer incorporated emulsion on a water-resistant, resin-coated base. In the processor, chemicals are used over and over again to produce a large number of prints. In other words, the processor uses a batch of processing chemicals until the operator replaces them with another batch. During operation, a small amount of activator solution is continuously added. This replaced the small amount of activator which is lost with each print. It is currently recommended that the chemicals be replaced after one week, i.e., five days of use, or after they have been employed to make one-thousand 8.times.10 inch (20.3.times.25.4 cm) prints or the equivalent, whichever occurs first.
Because of the use conditions associated with automated processors, development of a toning agent for such devices is a difficult task. This is especially true when a high degree of uniformity and controllability of image tone are among the objectives. For example, as stated above, such a processor is designed to prepare a large number of prints before the batch of chemicals is replaced. Hence, the toner chemical must perform in substantially the same way, time after time, in a constantly changing environment. One reason why the environment is constantly changing is the buildup of by-products of development produced each time the activator is used. Thus, the toner chemical must operate in the same way when there is no, little, some, or much by-product (from the development process) available in the solution in which the toner is employed. Moreover, toner chemical, and by-product(s) therefrom are carried downstream with each print. These materials should not harm the downstream operations.
Applicant set out to develop a system which would provide a cold image tone in black-and-white photographic prints made (from papers which did not provide such a cold tone) by a high speed automated processor (such as the aforementioned commercial unit). He also set out to develop a system in which the image tone remained within a relatively narrow tone range over the recommended useful life time of the chemicals used, i.e., over a relatively large number of prints. During the course of his studies, it was discovered that incorporation of potassium iodide in the activator solution unexpectedly accomplished both goals. It is believed that this discovery provides a significant advance in the art.